Web Performance Calendar day 31 article 4/5: @twnsnd.com on Compression Dictionaries to dramatically shrink responses (60–90% smaller than Brotli/GZIP). Why adoption is slow. Practical architectural decisions and implementation tips to get huge bandwidth wins. calendar.perfplanet.com/2025/from-th...

TIL: Compression Dictionary Transport 💡 A new HTTP feature that can dramatically shrink the size of your responses, especially when serving content that changes often but includes a lot of repeated structure (think: JSON, JS, CSS). Learn more 👇 developer.mozilla.org/en-US/docs/...

If you haven't tried it yet, Nano Banana Pro does a stunningly good job of creating caricatures. Give it a photo (or several) and a theme or elements to incorporate and let it go. Then tweak as needed.

🤔 What are request priorities, and why do we even need the HTML fetchpriority attribute? Check out my new video to find out! www.youtube.com/watch?v=yoa7...

🎙️LET'S GET READY TO RUMBLE! It's been one of DevTool's most requested features… weighing at eiiighty-five votes… 10 years in the making… entering the ring from Chrome 144… Heeeerre's: Individual request throttling!!! developer.chrome.com/blog/throttl... 🥊 It's a knockout! The crowd does wild! 👏🙌🎉🥳

Implemented shared compression dictionaries [1] on an @11ty.dev site. Nothing in production to share yet, but shows HTML responses being ¼–⅓ the size of @netlify.com's dynamic Brotli-compression. ~4-6kb per page inc. inlined CSS, before any tuning 🤯 [1]: chromestatus.com/feature/5124... #webperf

Fellow #perfnow fellows, a reminder that PerfPlanet calendar is coming this December for another edition. And it needs YOU. Please ask if you have any contribution ideas or concerns calendar.perfplanet.com/contribute/

Interesting! Etsy implemented speculation rules and got these results: 👍 Time to First Byte on the listing page improved 23.6% 👍 First Contentful Paint improved 20.7% 👍 Largest Contentful Paint improved 21.1% 👍 DOMContentLoaded improved 20.4% #PerfNow #webperf www.etsy.com/codeascraft/...

I've been writing more about how Web Standards *actually* come to be, and the responses make me thing there's a ton more to discuss; so in the spirit of figuring it out together, AMA: infrequently.org/series/effective…

Glad to announce that my team at @cloudflare.social released a 1.0.0 version of a cross-browser web performance testing agent that supports Chrome, Firefox, Safari and Edge. Thank you to @tkadlec.bsky.social for making it happen and writing most of the code so far! github.com/cloudflare/t...

I am at #perfnow the next two days. Drop by the Google help desk if you want to chat about the Devtools MCP server or our performance agent in Devtools.

Really excited to be speaking @perfnow.nl this year—my favourite conference run by some of my favourite people! If you're into web performance (or wanna be!) and like a great conference with a super friendly vibe then pop along to Amsterdam at the end of October. Tickets selling fast! perfnow.nl

I put together a whole page of resources and pointers on these topics, and cannot recommend "Life of a Pixel" often or highly enough: infrequently.org/links/#web-p...

"How is it possible for CrUX to say 90% of page loads are good, and Google Search Console to say only 50% of URLs are good. Which is right?" It's a question I get about Core Web Vitals and I admit it's confusing, but the truth is both are correct because they are different measures... 1/5 🧵

Fun times when the AI support chatbot hallucinates ACTUALLY placing an order for a replacement item that didn't get delivered. The actual conversation feels completely effortless until days later when you figure it out because it still hasn't arrived.

Tune in this Wednesday to learn more about the latest WordPress Core Performance Team efforts, including the View Transitions plugin!

This is what makes @perfnow.nl so awesome to attend. The hallway track is unbeatable (not just Googlers - Mozilla, Cloudflare, Akamai, Shopify, Speedcurve, etc....). Attendees opt-in to being listed so you can get a sense for who has registered so far: perfnow.nl/attendees.html

Firefox shipping scheduler.postTask() and scheduler.yield() for all your long task-avoiding scheduling needs!!

💣 Working with a retail client recently, we were able to work out that a regression cost them **23% in relative conversions**—a huge loss. The business prioritised an immediate rollback. Before our project, not only would the regression have gone unnoticed, they’d have no idea its impact.

performance.now(), the web performance conference, 30th and 31st of October, Amsterdam. Single track, the best speakers in the industry, plenty of your performance-mad peers around to have fascinating conversations. What's not to like? Let's introduce our speakers ... perfnow.nl

I was excited when @speedcurve.com reached out to me to build their #Shopify app - now it's easier to integrate full real-user performance data collection in Shopify storefronts and correlate that data with bounce rates and conversions. Now you can see exactly how #webperf impacts your bottom line!

what tech companies *haven’t* done layoffs in the last 3 years? it’s time for a goodwill thread

Compression Dictionaries are my new favourite thing in #webperf! Check out this new Case Study about how Google Search uses this new technology, which also explains exactly what this is and how it works using them as an example: developer.chrome.com/blog/search-...

Wow, replacing a destroyed iPhone is quite the ordeal. You can't log in to restore backup since it needs to text a verification code to the phone that isn't set up yet if you don't have another iOS device. And you can't set up cellular before restoring a backup.

Fascinating deep dive by @iamtk.bsky.social on tracking down an LCP issue: www.iamtk.co/optimizing-n... It’s a lot of work for what some might see as a small gain, but uncovered (and fixed!) real issues that might otherwise have gone unnoticed.

Is there anyone who DIDN'T see this coming? This wasn't nation-state and wasn't the cabinet member's history but I'd be surprised if those weren't compromised long ago, just a lot more quietly. techcrunch.com/2025/05/05/t...

For the compression curious, this is a neat visualization of what gzip does - andrewiggins.github.io/gz-heatmap/?... - via @paul.irish

I kind of wonder what the next level of attack surface is going to look like. Intentionally seeding AI crawler results with a significant amount of "looks right but is malware" kind of attack? Running random AI models locally not so "safe" in that case either.

For those monitoring Core Web Vitals, we made a small change to the CrUX History API used by CrUX Vis last night and now return 10 months of data, rather than 6 months of data to bring it more inline with the CrUX Dashboard that we're looking to deprecate. Enjoy! cruxvis.withgoogle.com#/

Compression Dictionary Transport: using shared compression dictionaries to reduce the transport size of HTTP responses @tunetheweb.com @developer.mozilla.org developer.mozilla.org/en-US/docs/W... #ECMAScript #JavaScript

Are browser IP-anonymization proxies just a less-secure private TOR network (with newer protocols)? Randomly thinking that modernizing TOR and providing a way to bill/pay for network access would be a better path than re-inventing a less-secure version. support.apple.com/en-us/102602

Compression Dictionary Transport allows you to DRASTICALLY reduce download sizes in Chrome. E.g. if you have app.v1.js and app.v2.js is released, a lot of the code is likely the same, so why download it all again? Want to know more? Check out this new guide: developer.mozilla.org/en-US/docs/W...

I'm excited about this program! Chromium isn't necessarily easy, but I know there are great engineers out there who would love to get paid for improving it!

📢 Call for Presentations I'm looking for the next speakers for the 11ty meetup! Speakers of all levels welcome! Got a talk idea related to 11ty and/or the indie web? Let me know! #11ty 11tymeetup.dev

New in Chrome DevTools: Accurately emulate CPU performance of a low/mid tier phone with Automatic CPU throttling calibration! 📲 This feature calculates slow-downs for your specific device. Wanted this for years! We just shipped it.

This is going to be brilliant to normalise different devices (especially you lucky folks working on high-spec dev laptops and desktop machines). Never knew whether to use 4x or 6x (or even the new 20x) slowdown? Now use the custom ones provided after a one-time calibration process. #webperf

Wrote a post on how Google Search uses Speculation Rules to prefetch search results: developer.chrome.com/blog/search-... They are using a number of the more niche features of the API, which some of you may not even be aware exist.

(1/2) Hello font-fancying folks, I'd like to gather data (and then release it in a form similar to caniuse) about the pre-installed fonts on each OS. The tool to gather the data (using queryLocalFonts, so Chrome-only) is fontes-locais.vercel.app, an example data: github.com/stoyan/fonte... ...

🚨 An upcoming client was hit by a sustained DDoS attack last week and needs to delay their February project. This means I have almost immediate availability for short-term, tactical engagements next month! DMs are open.

Let's celebrate our first #webperf hero of 2025: @anniesullie.com! @cliffcrocker.bsky.social caught up with Annie to talk about big wins in 2024, what she and her Speed Metrics team are working on now, and what she sees as the biggest challenge in front of us. www.speedcurve.com/blog/perform...

Are you a web designer or developer with a wish list for Safari/WebKit? What’s on it?

Hmm, interesting - looks like Chrome added support for the ORIGIN frame for HTTP/3 (eliminating the need for a DNS lookup before coalescing connections). blog.chromium.org/2024/12/maki...

It's pretty incredible just how far ahead of everyone else Cloudflare is with their workers platform, and how much they've OSS'd w/ Workerd. This is the heart of strategy: knowing the minds of your competitors so deeply that you can predict they won't follow your lead until it's *way* too late.

Excited to be able to contribute to the annual perf calendar. Thanks @stoyan.org for the tireless efforts you put into wrangling authors every year. If you haven't visited yet, go back through the archives. There's 15 years of awesome (and still relevant) content.

My talk from this year's We Love Speed is on YouTube! 👇 In "Tight Mode: how browsers REALLY load web pages", I take a very deep/very nerdy dive into why browsers sometimes intentionally delay loading resources, why they all do it differently, and why they should *stop clowning around* 🤡 #webperf

Web Performance advent day #5 with @karlijnlowik.bsky.social sharing the experience of talking to stakeholders (CEOs, SEOs...) about web performance and what we can do to get better at it calendar.perfplanet.com/2024/sux-sel...

Spotted in the wild - Dictionary content-encoding for display ads. Pretty sure the feature usage chart for dictionary encoding is about to take a pretty big jump.

This year's web perf calendar is off to an excellent start with Noam reminding everyone about Goodhart's law and the importance of remembering _why_ we're optimizing for perf in the first place calendar.perfplanet.com/2024/goodhar...

I've been threatening to write a post for awhile now about how elegant standards like Speculation Rules are, as they are built in a way that provides an natural progression for rolling out. @csswizardry.com does an _excellent_ job of demonstrating it in his latest: csswizardry.com/2024/12/a-la...